A .dat extension only means “data”; it does not identify one specific file format. Excel can open or import a DAT file when the contents are actually text-based tabular data, but a binary DAT file from another application may be unreadable in Excel.
Inspect the source before importing
If you know which program created the DAT file, check that program’s documentation. A file containing readable rows separated by commas, tabs, semicolons, or another delimiter is a good candidate for Excel’s text import tools.
Import a text-based DAT file
- Open Excel and start a blank workbook.
- Use Excel’s Data import controls for text/CSV data.
- Select the .dat file. You may need to change the file filter so it is visible.
- Choose the correct delimiter, encoding, and column interpretation in the preview.
- Load the data into the worksheet.
Protect identifiers and dates
Account numbers, ZIP codes, product IDs, and other values with leading zeros should often be imported as text. Also inspect dates because Excel can interpret ambiguous day/month formats incorrectly.
Do not rename a DAT file to XLSX
Changing the extension does not convert the internal data. After a successful import, save the workbook as .xlsx if you want an Excel workbook.
Binary DAT files need their original software
If opening the file in a text editor produces unreadable binary content, Excel is probably not the appropriate program. Use the application that created it or an official export/conversion feature.
Keep an untouched copy
Work from a copy when the DAT file is important. That preserves the original if an import or conversion produces unexpected results.
Matt Jacobs has been working as an IT consultant for small businesses since receiving his Master’s degree in 2003. While he still does some consulting work, his primary focus now is on creating technology support content for SupportYourTech.com.
His work can be found on many websites and focuses on topics such as Microsoft Office, Apple devices, Android devices, Photoshop, and more.